Case study: a Cardiff Victorian terrace with knotweed under the back wall
A pre-sale instruction, a four-week turnaround, and a buyer who never asked a second question.
A two-bed Victorian terrace in Roath, on the market at offers over £315,000. The buyer's surveyor flagged a single stand of Japanese knotweed in the rear garden, growing through a section of the boundary wall and within two metres of the kitchen extension. The sale was on hold pending a management plan.
Site visit
Survey within four working days of the call. A single mature stand, roughly 4 square metres above ground, with rhizome probably extending under the boundary into the neighbour's garden. The neighbour was cooperative — they had assumed it was bamboo for several years.
The recommendation
Excavation was not viable: the stand was tight against the kitchen footing and a Victorian masonry wall the seller did not want to disturb. A five-year stem-injection herbicide programme with a 10-year insurance-backed guarantee was quoted at £2,650 + VAT, with the first treatment in the same growing season.
The paperwork pack
- Survey report and identification confirmation.
- Method statement and five-season treatment schedule.
- Quote, signed contract and 10-year IBG certificate.
- Letter to the neighbour offering to extend treatment to their side at cost.
Outcome
Pack delivered to the seller's solicitor inside three weeks of the original call. The buyer's lender — Nationwide — confirmed they were comfortable to proceed within 48 hours of seeing the IBG. Sale completed at the original asking price. We are now into season three of treatment, with stem counts down 94% on the year-one baseline.
“The whole thing was a non-event in the end. Without their paperwork we would have lost the sale or knocked five grand off the price.”
Reviewed by
The survey team
PCA-certificated surveyors, Japanese Knotweed Elimination
PA1 / PA6A certificated surveyors who carry out the site visits, write the management plans and sign off the reports issued to lenders and solicitors.
Reviews the technical, legal and lender statements in this article.
What this page can't tell you
- Guidance is general. Identification, treatment choice and timescales can only be confirmed by a site visit — photographs alone are indicative.
- Lender and insurer requirements vary by institution and change over time. We state what is typically accepted, not what any named lender will accept on your case.
- Guarantee (IBG) eligibility depends on the plan chosen, the survey findings and the underwriter's acceptance. It is not automatic.
- Legal points summarise published law and guidance current at the review date. They are not legal advice.
Last reviewed · Questions on anything stated here: 07582 869979
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